Compliance to PyDB API 2.0¶

Full text of Python Database API 2.0 (PEP 249) is available at http://www.python.org/dev/peps/pep-0249/

Unsupported Optional Features¶

Cursor.nextset

This method is not implemented because the database engine does not support opening multiple result sets simultaneously with a single cursor.

Supported Optional Features¶

Connection.Error, Connection.ProgrammingError, etc.

All exception classes defined by the DB API standard are exposed on the Connection objects as attributes (in addition to being available at module scope).

Cursor.connection

This read-only attribute return a reference to the Connection object on which the cursor was created.

Nominally Supported Optional Features¶

Cursor

arraysize

As required by the spec, the value of this attribute is observed with respect to the fetchmany method. However, changing the value of this attribute does not make any difference in fetch efficiency because the database engine only supports fetching a single row at a time.

setinputsizes

Although this method is present, it does nothing, as allowed by the spec.

setoutputsize

Although this method is present, it does nothing, as allowed by the spec.

Caveats¶

Firebird-driver offers a large feature set beyond the minimal requirements of the Python DB API. This section attempts to document only those features that overlap with the DB API.

Connection

commit(retaining=False) rollback(retaining=False, savepoint=None)

The commit and rollback methods accept an optional boolean parameter retaining (default False) that indicates whether the transactional context of the transaction being resolved should be recycled. For details, see the Advanced Transaction Control: Retaining Operations section of this document. The rollback method accepts an optional string parameter savepoint that causes the transaction to roll back only as far as the designated savepoint, rather than rolling back entirely. For details, see the Advanced Transaction Control: Savepoints section of this document.

Cursor

description
Firebird-driver makes absolutely no guarantees about description except those required by the Python Database API Specification 2.0 (that is, description is either None or a sequence of 7-element sequences). Therefore, client programmers should not rely on description being an instance of a particular class or type. Firebird-driver provides several named positional constants to be used as indices into a given element of description . The contents of all description elements are defined by the DB API spec; these constants are provided merely for convenience.
DESCRIPTION_NAME
DESCRIPTION_TYPE_CODE
DESCRIPTION_DISPLAY_SIZE
DESCRIPTION_INTERNAL_SIZE
DESCRIPTION_PRECISION
DESCRIPTION_SCALE
DESCRIPTION_NULL_OK
Here is an example of accessing the name of the first field in the description of cursor cur:
nameOfFirstField = cur.description[0][firebird.driver.DESCRIPTION_NAME]
For more information, see the documentation of Cursor.description in the DB API Specification.
rowcount

Although Cursor in Firebird-driver implement this attribute, the database engine’s own support for the determination of “rows affected”/”rows selected” is quirky. The database engine only supports the determination of rowcount for INSERT, UPDATE, DELETE, and SELECT statements. When stored procedures become involved, row count figures are usually not available to the client. Determining rowcount for SELECT statements is problematic: the rowcount is reported as zero until at least one row has been fetched from the result set, and the rowcount is misreported if the result set is larger than 1302 rows. The server apparently marshals result sets internally in batches of 1302, and will misreport the rowcount for result sets larger than 1302 rows until the 1303rd row is fetched, result sets larger than 2604 rows until the 2605th row is fetched, and so on, in increments of 1302. As required by the Python DB API Spec, the rowcount attribute “is -1 in case no executeXX() has been performed on the cursor or the rowcount of the last operation is not determinable by the interface”.

Note

This attribute is just an alias for Cursor.affected_rows property.